Investigation of Heterogeneous Catalysts by an Electrochemical Method: Ceria and Titania-Supported Iridium Nanoparticles for Ethylene Oxidation

Abstract

Recently, metal support interaction (MSI) has been demonstrated to be closely related to electrochemical promotion of catalysis (EPOC) in the functionality of the process through spillover/backspillover of ionic species to/from the conductive support. In the present work, the interaction that iridium oxide (IrOx) nanoparticles have with two mixed ionic-electronic conducting (MIEC) materials (i.e., ceria, CeO2 and titania, TiO2) for ethylene oxidation is evaluated. To this end, the open circuit catalytic oxidation of ethylene as well as steady-state polarization measurements were carried out for free-standing (unsupported) IrOx and ceria- and titania-supported IrOx (~1 nm). The presence of these two supports was found to increase the catalytic reaction rate when compared to the free-standing IrOx, and decrease the electrochemical reaction rate at the three-phase boundary, as confirmed by the exchange current density (i0). In the light-off experiments, the IrOx/CeO2 catalyst showed a higher reaction rate until 3000C; however IrOx/TiO2 was superior at 3500C. It was also shown that the catalysts with lower i0 resulted in higher open-circuit reaction rates due to the larger amount of thermally-induced backspillover promoters to the gas exposed catalyst surface, in agreement with the EPOC phenomenon.

Electrochemical Promotion of Nanostructured Palladium Catalyst for Complete Methane Oxidation

“…The resulting total metal loading was 0.5 mg of Pd on YSZ. Catalytic measurements were carried out at atmospheric pressure in the single-chamber capsule reactor reported earlier [31,32]. The working electrode side of the electrolyte was pressed against a gold mesh (1 cm 2 ) that served as a current collector, while the counter and reference electrodes were pressed directly against gold wires [33].…”

Isotopic Oxygen Exchange Study to Unravel Noble Metal Oxide/Support Interactions: The Case of RuO2 and IrO2 Nanoparticles Supported on CeO2, TiO2 and YSZ

“…Metal oxide nanoparticles (RuO 2 and IrO 2 ) were prepared using the polyol method to obtain a narrow range of particle size distribution. [10,32] The synthesis involved, 0.11 g of H 2 IrCl 6 (Alfa Aesar®, � 99.99 %) or 0.21 g of RuCl 4 (Sigma-Aldrich®, � 99.99 %) dissolved in 50 mL of ethylene glycol with 0.08 M of NaOH. The solution was refluxed at 160°C for 3 h, resulting in a pH drop from 10 to 7.5, indicating nanoparticles formation.…”

“…The solution was refluxed at 160°C for 3 h, resulting in a pH drop from 10 to 7.5, indicating nanoparticles formation. The NPs colloid solution was mixed with a pre-calculated amount of the supporting metal oxide powder in deionized water for 72 h. [32,33] The mechanical attachment of the nanoparticles (NPs) to the supporting metal oxides is signaled by the change of the solution's color to clear when the solid phase sediments upon cessation of the mixing. The catalyst sludge is centrifuged and dried in a freeze dryer (LabConco®).…”

“…Four-port valves were used to switch the feed inlet to the reactor between pre-treatment conditions and reactants feed. Another four-port valve would allow the feed gas to enter the reactor or by-pass it before it continues its flow to the Hiden® quadrupole mass spectrometer where the gas composition is detected by following the masses of 18,20,28,29,32,34,36,42,44, 46 m/z.…”

Controllable Synthesis and Growth Mechanism of Ceria Nanocubes by Template‐Free Hydrothermal Method

“…Many synthetic methods have been reported, including spray pyrolysis method, [14,15] ultrasound and microwave assisted pyrolysis method, [16] electrochemical method, [17,18] Homogeneous precipitation method [19,20] and so on. Based on these methods, different morphologies of CeO 2 have been fabricated, such as nanorods, [21] nanotubes, [22,23] nanowires, [24,25] microplates, [26] and spherical CeO 2 .…”